FR2818438A1 - TRANSMITTER STRUCTURE FOR FIELD EMISSION DISPLAY - Google Patents

Abstract

The present invention relates to a field emitter network used for various types of devices, comprising a display device based on nanotubes, and a microwave amplification device. In interior art, an electron strikes a phosphor (28) on the screen to emit light, a positive ion released from the phosphor (28) strikes the emitter, whose structure can be deformed or destroyed. According to the present invention, there is a carbon nanotube (10) and it is coated with a very thin layer of a semiconductor or insulator material (12) having a high degree of hardness; the carbon nanotube is protected from external particles (in particular positive ions), and the electrons are emitted easily under a lower applied voltage, which considerably improves the uniformity and the stability of the emission of electrons.

Description

FIELD OF THE INVENTION

  The present invention relates to a field transmitter for various types of devices comprising a display device with

  nanotube base and a microwave amplification device. More by-

  In particular, the invention relates to a field emitter using a carbon nanotube as the emitter material in a display device using a field emitter. Here, the term "display device" is intended to cover all other display devices

using a field emitter.

BACKGROUND OF THE INVENTION

  A field emission display device (AEC), the principle of which was already introduced in 1968, has been the subject of continuous research and development as a display device following the

  TRC (cathode ray tube), TFT-LCD and large screen PDP.

  In such a field emission display device, one of the most important elements is a field emitter which is equivalent to the electron gun of a TRC, and it has been considered, as a material for making it, a metal (mainly molybdenum), a

  semiconductor, diamond and the like. Since a suggestion

  tion regarding the use of a carbon nanotube as a material

  transmitter, was made around 1995, research was carried out

  che and a development associated with the use of the nanotube

  bone. The use of the carbon nanotube as an emitter has the advantages that the emitter of the carbon nanotube is much thinner than a emitter conventionally used, that a high electric current is created by applying a low voltage, that the redundancy due to the fact that there are a large number of spikes in it, and that the carbon bonding characteristics guarantee a higher structural stability than with an emitter

made of metal.

  Approaches for the fabrication of the nanotube

  bone, which have been suggested so far, include the following approaches

lowing:

  first, we grow nanotu- vertically

  bes of carbon on a substrate by passing hydrocarbons over the substrate covered with a catalyst such as nickel and the like, using a chemical vapor deposition (CVD) process; secondly, carbon nanotubes are abundantly created using an arc discharge or a laser ablation method commonly used in the prior art, they are mixed with another metallic adhesive agent, then the mixed material is placed on the substrate; and

  third, we form a set of nanotubes of car-

  bone parallels by applying a polarization to immersed aluminum

  aged in an acid solution, and allowing the aluminum oxide film to erode continuously to obtain fine holes regularly perforated thereon (using what is called an alumina process

  anode), then passing hydrocarbons through the holes.

  Figure 1 shows a schematic representation of a

  conventional carbon nanotube (uncoated) in which a

  che indicates the direction of the electrons (-e) emitted when a voltage is applied to the carbon nanotube used as cathode. In practice,

  there are a large number of nanotube tips but we have not shown

  felt here only one representative nanotube.

  Despite the development efforts of such nanotubes, it

  there is the big problem that during use the structure of a na-

  notube can be deformed or destroyed, thus leading to an insta-

  bility or to an interruption of its operation.

  The main reason why a transmitter works

  is put out of use, is that when an accelerated electron

  comes to strike a phosphorus to emit light, an ion po-

  The ejected phosphorus is accelerated in the opposite direction and strikes the emitter. For this reason, uniformity, stability and durability

  of a display screen do not reach a level required for use

commercial station.

SUMMARY OF THE INVENTION

  Therefore, in view of the above problems, the pre-

  sente invention aims to create a field emission transmitter

  carbon nanotube, which is able to improve considerably

  the performance of a display device with emission of

  field by covering a tip of the carbon nanotube with a layer

  semiconductor or insulator having a high degree of hardness for a thin thickness, of the order of a few nanometers (nm), so as to protect the tip from the emission of electrons coming from a collision with the outer particles, thereby establishing the durability and stability of the carbon nanotube, as well as reducing the tension

applied to it.

  According to an embodiment of the present invention, a field emitter comprises a semiconductor layer or

  insulation deposited thereon by evaporation of the semi-layer

  conductor or insulator on the carbon nanotube using a pro-

  yielded by electron beam evaporation.

  According to another embodiment of the present invention

  tion, a field emission transmitter comprises a semi- layer

  conductor or insulator deposited on the carbon nanotube by spark-

  celing of argon on a semiconductor or an insulator, projection of the constituent atoms, and injection of these atoms on the nanotubes of

carbon.

  According to other features of the invention, the material

  link of semiconductor or insulator deposited on the nanotube of

  bone is doped with type n so as to reinforce the conduction of electrons in the case where the material can be doped with type n. In

  variant the semiconductor or insulator material is any one

  than materials comprising various types of compounds B, C, N in-

  cluting a BN, a carbon analogous to diamond and diamond, various

  types of oxide insulating materials, and various iron body parts

  which have a high degree of hardness and a high durability

  against collisions of atoms or molecules.

  In addition, it is possible to deposit a layer of semi

  conductor or insulator on a carbon nanotube using all the methods used to form a very thin molecular layer, such as for example a laser ablation process, a DVC process

conventional and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

  The present invention will be described below in a manner

  more detailed using the embodiments shown in the

  attached sins in which: - Figure i is a schematic representation of a conventional carbon nanotube in which an arrow indicates the direction of emission of electrons; - Figure 2 shows a schematic structure of a field emitter according to the present invention, in which a carbon nanotube is protected from collision with atoms or particles

  external by a thin layer of semiconductor or insulation

  placed on it; - Figure 3 is a schematic representation of a field emission amplification by a field emitter structure according to the present invention; and - Figure 4 is a schematic representation of the use of a field emission tip mounted on a display device to

  field emission according to the present invention.

  DETAILED DESCRIPTION OF THE EMBODIMENT

PREFERENTIAL

  Figure 2 is a side view of a field emitter according to a preferred embodiment of the present invention. In

  practical, there are a large number of nanotube tips of car-

  bone, but only one point of nanotube represented here has been represented

  sentative. In addition, although a simple nanotube, called nanotube 5.5 is shown here by way of example, the same result is obtained in the case of a nanotube having a different winding shape and a different size, likewise than a single wall or multiple wall structure.

  Using a coating process as described above

  above, the carbon nanotube is coated with a semi-layer

  conductor or insulator 12 of very high hardness, which is n-type doped and has good durability against collision with external atoms or particles (usually positive ions), for a thickness of a few nanometers (nm). For coating applications, types of compounds B, C, N including BN, GaN, Si3N4, TiC, B4C, etc., types of oxides including TiO2, A1203, MgO, etc., and body parts can be used. ferroelectric including SrTiO3, etc. It is possible to use diamond-like carbon particles (CAD) or diamond particles, without performing n-type doping. External particles such as, for example, atoms or positive ions 14 dropped from phosphorus, can collide with the semiconductor or insulator layer 12 and rebound

  on it or be adsorbed on its surface.

  During this time, if a bias voltage is applied

  applied from the outside to the carbon nanotube, a strong electric field is produced on the tip of the carbon nanotube. In that case,

  due to a potential distribution inside the coating material

  The potential energy becomes lower in proportion to the distance from the tip of the carbon nanotube, and the potential barrier

  is reduced. As a result, as shown in Figure 3, a strong emis-

  Electron ion can be induced under a low bias voltage.

  tion. As the semiconductor or insulating layer has dielectric properties, if a voltage is applied to the layer, positive charges 18 are induced around the carbon nanotube and negative charges 20 are induced on the surface of the layer of semiconductor or insulator. As a result, as indicated by the arrow

  22, a large number of electrons are emitted out of the semi-layer

  conductor or insulator, compared to the case of Figure 1 o the carbon nanotube was not coated. Under n-type doping, a

  new electron conduction occurs in the semi-layer

  conductor or insulator, which smooths the flow of electrons. In addition, by making the semiconductor or insulation layer as thin as

  possible, the diffusion of electrons is greatly reduced.

  Figure 4 is a schematic representation of the use of a field emission tip mounted on a field emission display device according to the present invention. Although the field emission tip according to the invention is built on an existing field emission display device, the emission tip

  of field is characterized in that it is formed by a network of na-

  carbon notubes finely coated with a semi-layer

  conductor or insulator, as shown in Figure 2.

  As shown in FIG. 4, a pixel consists of an anode plate 30 coated with a phosphor 28, field emission spikes formed of carbon nanotubes coated according to the present invention, and spacers 34 between which a small vacuum interval is maintained. In addition, a field emitter network panel (REC) constructed by pixels arranged in two dimensions, comprises a cold cathode plate 26 mounted on a glass substrate 24. A metal grid 36 placed between the cold cathode 26 and the anode plate 30, controls the amount of electrons emitted from the cold cathode plate 26 to the anode plate 30. Horizontal and vertical electrodes are arranged on the cold cathode

  26, and the REC is addressed by matrix through the electors

  trodes. As a result, during the time during which a voltage is applied

  that at the metal grid 36, electrons are emitted and then accelerated by

  the anode voltage applied to the anode plate 30. Next, the electri

  trons pass through the vacuum gap and strike the phos-

  phore deposited on the anode plate, thereby producing an emission of light. Reference 32 indicates a conductive glass (tin oxide

  indium: OEI) covering the anode plate.

  The remarkable feature of the present invention is to protect the carbon nanotube from collisions with external particles (mainly molecules or atoms having a positive charge). As shown schematically in Figure 2, of

  fact that the carbon nanotube is protected by the semi-material

  conductor or insulator with good durability against colli-

  Thanks to its very solid bonding characteristics, the coated carbon nanotube produces an emission of electrons which is done in a stable and continuous manner, thus considerably improving the gloss.

  of a display device and its durability.

  As described above, by coating the tip of the nato-

  carbon tube by a thin layer of semiconductor or insulator having n-type doping and a high degree of hardness, one can

  protect the carbon nanotube from collisions with particles ex-

  dull, and we can greatly increase the emission of electrons under a

  low voltage applied. As a result, the field emitter formed of the na-

  carbon notube according to the present invention can be greatly enhanced

  improved in durability and stability, just as it can be controlled by a low applied voltage. As a result, the field emitter according to the present invention can be effectively applied to the manufacture of

  various kinds of field emission type display devices.

Claims (4)

  ) Field emitter, characterized in that it is formed by evaporating a semiconductor or insulating material on a carbon nanotube (10) by means of an electron beam evaporation process, and by depositing the semiconductor layer or   of insulation (12) on this carbon nanotube.   2) Field emitter according to claim 1, characterized in that the emitter is formed by depositing a layer of semiconductor or insulator (12) on the carbon nanotube (10) by means of a process of argon sparking.   3) Field transmitter according to claim 1 or 2, characterized in that   the semiconductor or insulator material (12) deposited on the nano-   carbon tube (10) is n-doped so as to reinforce the conduction of electrons in the case where the material can be doped of type n.   4) Field emitter according to claim 1 or 2, characterized in that the semiconductor or insulating material is a material chosen from the group comprising compounds B, C, N including a BN, a   carbon analogous to diamond, diamond, various types of oxides iso- lants.